[php] haxe.io.Bytes.getString issues

[Aurel300]

class Main {
  static var validBytes = haxe.io.Bytes.ofHex(
    "010A" +
    "7F0A" +
    "C2800A" +
    "DFBF0A" +
    "E0A0800A" +
    "ED9FBF0A" +
    "EE80800A" +
    "EFBFBD0A" +
    "F09F9882F09F9884F09F98990A" +
    "C8A70A"
  );
  
  static function main():Void {
    Sys.println(validBytes.getString(0, validBytes.length, UTF8));
  }
}

$ haxe --main Main --php out
$ php7.2 out/index.php | xxd
0000000: 010a 7f0a c280 0adf bf0a e0a0 800a ed9f  ................
0000010: bf0a ee80 800a 0a                        .......

This also works with shorter strings; it's not that a particular codepoint causes it to stop parsing. I think the problem is that the string length is incorrect if there are any non-BMP sequences.

[Aurel300]

I think your commit broke the CI. https://travis-ci.org/HaxeFoundation/haxe/jobs/524202748